Lymphedema and ischemia are debilitating conditions for which limited treatment is available. Despite significant research, current treatment schemes are inadequate. In some instances, intradermal and subcutaneous delivery procedures have been tried, such as drug delivery, contrast agent delivery, gel and scaffold delivery for aesthetic and cosmetic applications, gel and scaffold delivery for repair and regeneration, cell delivery including cell plated on scaffold and gel.
Examples of common delivery methods which penetrate the skin to very small depths (0.5-1.0 mm) include a) jet injection, including needle-free injection and b) microneedles patch delivery. Standard subcutaneous methods for short distance injections would be the Mantoux technique (standard intradermal delivery method) or BD microinjection system.
However, these methods cannot be directly applied for the delivery of relatively large medical devices (millimeters and sub-millimeters size) or devices that have to be delivered into a large area in the mammalian body. For example, special methods are needed for intradermal delivery of a 100 mm long and 0.3 mm thick thread-like scaffolds. Thus, such procedures are very limited.
Another important need is the delivery of cells and growth factors into an ischemic mammal leg for treatment of critical limb ischemia. Current cell delivery systems have critical limitations, such as for example: inefficient cell retention and lack of targeted localization. Collagen, fibrin, gelatin, alginate, and matrigel have been studied as cell delivery vehicles in the form of injectable gels or three-dimensional scaffolds. While many of these materials have shown potential for success, they are not without their limitations. The issue of cell and material retention in injectable gels, as well as vascularization and nutrient diffusion in three-dimensional scaffolds, remains a challenge. The fibrin microthreads proposed recently by Cornwell and Pins have overcome these problems, but they have low mechanical strength and high degradation rate, and thus have very limited suitability. Accordingly, there is significant need for further advancement and development.